“We heard some news about people who are arrested at night and we are worried if it could happen to us,” a Tehran resident active in the protests wrote in an e-mail Friday, asking for anonymity for fear of government retaliation.

The targeted arrests appear to have begun the day after the election. Several of Iran’s best-known reformist politicians were taken into custody, including the brother and several close allies of former President Mohammad Khatami.

Since then, at least 230 more students, professors, journalists and reformists have been arrested, according to the International Campaign for Human Rights in Iran. At least 29 are known to have been released, the New York-based organization said in a list released Wednesday, although it acknowledged that the numbers were constantly changing.

The crackdown appears to have grown bolder as the government escalated its use of force on the streets.